1. Technical Field
The present invention relates to a tubular burner having; a mixing tube including at a rear end thereof an inlet port into which a fuel gas and primary air flow; a venturi section having a smaller diameter than the diameter of the inlet port; and a tapered tube section having a gradually larger diameter from the venturi section toward a front of the mixing tube. The tubular burner has a flame hole member with a plurality of flame holes, the flame hole member being adapted to be fitted into a front end region of the mixing tube.
2. Background Art
As this kind of burner, there is conventionally known one which is described in U.S. Pat. No. 5,186,620. In the burner as described therein, a flame hole member is made of a sintered metal of larger thickness. A plurality of flame holes which penetrate in the forward and backward (i.e., longitudinal) direction are formed in the flame member so that a mixture of a fuel gas and primary air (hereinafter also referred to as air-gas mixture) is ejected from these flame holes for combustion.
The flow of the air-gas mixture that flows from the mixing tube toward the flame hole member has a directional component that is directed radially outward under the influence of the tapered tube section. Therefore, if the flame hole member is made smaller in thickness, the flame is more likely to get spread radially outward. In the above-mentioned conventional burner, on the other hand, since the flame hole member has a larger thickness, the flow of the air-gas mixture is rectified at each of the flame holes so as to be directed forward, thereby preventing the flames from getting spread radially outward.
However, in the above-mentioned conventional burner, the flame hole member is made of a sintered metal of higher material cost, thereby bringing about a disadvantage of higher cost.